The present invention relates to an internal combustion engine, comprising an inlet manifold and an exhaust manifold, respectively, opening into inlet ducts and exhaust ducts, respectively, to the engine cylinders, a charging unit, the pressure side of which is connected to an inlet air conduit opening into the inlet manifold; and a conduit for recirculation of exhaust from the exhaust side of the engine to its inlet side.
In supercharged internal combustion engines, e.g. turbo engines, the charged pressure of the intake air in the intake manifold is often higher than the mean pressure of the exhaust in the exhaust manifold, which means that conventional shutter and valve devices used in suction engines cannot be used in supercharged engines to transfer exhaust to the pressure side of the compressor. It is known to achieve this to use some type of pressure increaser on the exhaust side, e.g. constriction in the form of a turbo unit with variable geometry, or some form of pump device.
If the principle of pressure increase is used, this means that the engine will work against a pressure with its entire exhaust flow to return only a fraction of the flow, approximately 10%, to the inlet side, which results in an undesirable loss of efficiency. The principle with the pump, in addition to the extra cost and complexity, involves a parasitic loss corresponding to the rise in pressure of about 10% of the exhaust flow divided by the efficiency of the pump, i.e. a total of approximately 20% of the exhaust flow times the rise in pressure.